


Fraternal Twins are Still Twins!

by Arlerted



Series: Oh, I Assure You, We’re Brothers! [1]
Category: Ao no Exorcist | Blue Exorcist
Genre: Family, Friendship, Gen, Rin and Yukio being brothers, Rin got rekt, Rin's silly ideas, Sibling Bonding
Language: English
Status: Completed
Published: 2017-02-26
Updated: 2017-03-05
Packaged: 2018-09-27 02:00:07
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,952
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9945368
Author URL: https://archiveofourown.org/users/Arlerted/pseuds/Arlerted
Summary: Take away their different hairstyle, different height, Yukio's stupid glasses, and Yukio's stupid moles and they will be the same person, right? They are twins, after all!--A story where Shima teases Rin for not being very twin-like with the young Sensei and Rin is determined to prove that Shima is wrong.





	1. Shima's Tease

**Author's Note:**

> Hello!  
> This is my first story in this fandom and I will probably cross-post this to FFN as well! 
> 
> There are a few things that you should know or be warned about before reading: 
> 
> \- In this story Rin and Yukio's hair are the same color: black  
> You can see my reasoning at this tumblr post http://papan-talenan.tumblr.com/post/157725662722/about-rin-and-yukios-haircolor
> 
> \- I try to keep the way characters addressed each other (Like how Shima calls Rin "Okumura-kun" or refer to Yukio as "Wakasensei" while calling Konekomaru "Koneko-san") because I think it is a nice and important features that shows their relationship with each others (How close they are, etc.)  
> If you don't really get it, don't hesitate to ask, I might be able to give a (shaddy) flash course of Japanese addressing system (to my knowledge)-- also I'm sorry if I get any of it wrong. 
> 
> \- Possible OOC-ness 
> 
> \- I'm not very good at description so this is mostly conversation-centric, also, English is not my first language, if you find any mistake I'll fix it faster than lightning! 
> 
> \- I'm not really sure where this story is within the manga timelines, sometime after Kyoto arc since they already accepted Rin as son of satan and before Shima's you-know-what arc (no spoiler!) 
> 
> \- I have a certain fondness toward ShimaxRin/ShimaxYukio so... there might be a teeny tiny leak. But don't worry! Nothing is intended to be romance in this fic! 
> 
> \- This is a part of series where I will put random Rin - Yukio brotherly fluff stuff, feel free to drop a prompt or request, I'll be happy to try and write it. 
> 
> \- If you sees any underlined/blue text just click it, I usually linked a screenshot/gif from manga/anime as visual  
> \- Reviews, comments, even flames are welcomed. Enjoy.

“Hey, Okumura-kun.” Shima put his pen down and rested his chin on the edge of the table. He stared at the _mount_ of papers and reference books in front of him.

“Hmm?” Rin answered with a hum. Right now he is too distracted with notes that Yukio gave him last week to pay much attention to Shima.

“Is it true that you and _wakasensei_ are twins?” Shima sat up straight, staring at him.

“Huh?” This time not only Rin but Suguro and Konekomaru all directed their attention to Shima.

“I-I mean, yeah, of course we know since long ago that you _are_ twins, but—” Shima shrug because they all are staring at him.

“Are you that bored, Shima?” Suguro rolled his eyes. He knew Shima is seeking distraction from these assignments.

“Yeah, these are not going to finish themselves, Shima-san.” Konekomaru added before going back to his own answer sheet. They know that Shima _can’t_ sit still for more than five minutes without letting out complains. Especially when they are stuck to doing school chores like this.

“Of course we are!” Rin scowled and slammed his pen to the table.

“Not you too, Okumura.” Suguro sighed as he picked up a few loose notes that got knocked to the floor by Rin.

Shima smiled because Rin takes his bait. Now they can talk and forget about all this for a moment, “For starters, you look nothing like him! _Wakasensei_ looked more… mature. Not to mention he is tall! Waaaaay cooler than you.” That smile turned into a smirk because teasing Rin is… well, fun!

“What?! That because Yukio and I are naternal twins!”

“Fraternal.” Suguro corrected. He glanced at Konekomaru which also put down his pen to look at the arguing boys.

“Now that you mention it, none of your traits are similar as well. Fraternal or identical, twins usually still share something in common.” Konekomaru jumped into the conversation, he is getting tired as well to be honest. They’ve been here for almost four hours and haven’t even tackled half of the assignments.

“Of course I don’t! I’m not a _scaredy-cat_ or crybaby like that four eyes!” Rin crossed his arms, “Also, if you pay attention, our face are similar!”

Shima stared at him. Konekomaru stared at him. Even Suguro finally gave up and stared at him.

“Well?”

“Nu’uh.” “I don’t see it.” “Sensei don’t have that kind of stupid expression on his face.” Shima and Konekomaru nodded to the last comment made by Suguro.

“Arrghh.” Rin ruffled his own hair in frustration, he stood up, “Wait here!” He got out from the dining room where they are sitting and runs to the room he shared with Yukio.

Rin rummaged through his drawer. It's full of random knick knacks, snacks, and candies. The other drawer contained failed test sheets with which he hides from Yukio. His third drawer contained some loose note. “Where is it…”

He moved to Yukio’s table beside him, noticing a note on top of it that said, _“I will be back by dinner. – Yukio”._ Rin rolled his eyes and mutters something about Yukio being too busy then opening the first drawer. There are small bottles and packages of various liquids, herbs, some gun cleaning kit. Nope.

Second drawer: official looking maps with Yukio’s name and ‘ _Class Test and Materials’_ written on it. “Oooh, what do we have here…” Rin opens the map. He was hoping to find some answer for Yukio’s assignment. What he find is another note: _“I will know if you look at the content of this map, Nii-san. And I will double—no **triple**_ _your assignments for the next months.”_ Rin felt a shiver down his spine and slammed the drawer shut.

Third drawer: Glasses. Lots of glasses. Nope. That’s [Yukio’s ](https://68.media.tumblr.com/f7c23cbf283b981c952a06ce9dd86af2/tumblr_olzz4oeTtz1u18nm9o2_r1_540.png)_[stash](https://68.media.tumblr.com/f7c23cbf283b981c952a06ce9dd86af2/tumblr_olzz4oeTtz1u18nm9o2_r1_540.png). _

Fourth drawer: Random small items that didn’t belong in any of the drawer. Rin spotted what he is looking for, grabbed it, and dashed out back to the dining room.

“Here, look at this!” He slammed [a photograph of Yukio and himself](https://68.media.tumblr.com/be1312067c717ebeb484a305c68e67a1/tumblr_olzz4oeTtz1u18nm9o1_500.gif). They were wearing what looks like a kindergarten uniform.

“Oh, _wakasensei_ looks so cute.” Shima chirped.

“It’s hard to imagine that he was also a child once.” Konekomaru stared at Yukio at that picture.

“That is ridiculous, of course he is.” Suguro also gave a comment, looking at Yukio, then Rin. One thing that he noticed is that Rin’s ears at that photograph are normal, not small and pointy. That is kinda sad.

“Look...” Rin pointed at himself, wide smile with a peace sign, then to Yukio’s glasses wearing face. “We look the same, right? Aside from hair style and his stupid glasses!”

“I suppose, yes.” Shima finally admitted, Suguro and Konekomaru nodding in agreement. Rin looked satisfied, of course he is, and Yukio is his twin brother after all. It's only natural that he wanted them to acknowledge it.

“But only in this picture. The current you and _wakasensei_ are still nothing alike.”

“Oh yeah? We’ll see! Come here again tomorrow at lunch and I’ll show you something!” Rin pointed at Shima, “Bring Shiemi and Izumo too, we all can have lunch here!” He smirked, gathering his papers, “I gotta go now!”

“What about our homework?” Suguro protested.

“You can do it here if you want! Yukio won’t be here till dinner and you can ask Kuro where the bathroom is if you wanna go!” Rin is heading out, struggling to carry all his stuff.

“But we have to finish this today, Okumura-kun!” As much as Shima hate this assignment, he still got the sense of responsibility.

“I’ll drag Yukio—here to help us with that tomorrow if you want! Bye!” He stopped in the middle of his sentence, almost like he’s trying to stifle a laugh.

  
“I can’t believe that idiot, leaving us here by ourselves…” Suguro returned his focus to the paper in front of him. If Rin can ask Yukio to do that, it will be a serious help for them, but of course he didn’t want to bother his teacher like that.

“This is your fault, Shima-san.” Konekomaru sighed and looked at Shima.

“Can’t deny that!” Shima scratched his head, “But don’t you think something interesting is going to happen? After all we’ve had nothing but homework these days, a little fun can’t hurt anyone.” He stretched his arm and yawned, “I’m done for todaaaay.”

The Kyoto Trio ended up being there for two more hours until Suguro finally gave up. Shima fell asleep on his seat long ago. Konekomaru tried to wake him up but Shima won't budge. At the end Suguro decided to leave him there and go back to their own dorm.


	2. Rin's Perfect Idea

**Summary for the Chapter:**

> Rin's idea is perfect, what could go wrong?
> 
> Small part with Rin's crush to Shiemi mentioned because that is canon, nothing's serious.

**Notes for the Chapter:**

> This chapter is a bit rushed and I must say that I'm not very happy with it. Please tell me if you have any suggestion on what to fix, really, anything's welcomed.

 

 ** _Rin! Wake up! You are late!_** Kuro meowed as he pawed Rin’s face, trying to wake him up.

“Shut up, Yukio, it’s Saturday.” He brushed Kuro’s paw away and pulled his blanket up.

 ** _Arghh, you asked me to wake you up as soon as Yukio go away! Rin!_** Seeing that his effort does not work Kuro transformed to the giant form and kicked Rin from his bed.

“Ouch! What the hell?!” He instinctively hold Kurikara, ready to unsheathed it.

**_Time to wake up!_ **

“Kuro? Oh riiiiight. I completely forgot.” His voice is a little hoarse. “How do I sound?”

**_Close enough._ **

Last night after Yukio is gone he tried to force his voice to mimic Yukio’s. As a result his throat is a bit sore now, but it actually sounded like Yukio’s when he caught a cold last month. Yes. Rin is going to dress up as Yukio! He think it was a _genius_ idea! Between me and you, no one will be able to guess that, **_right_?** This will show them!

Rin took his phone and sent a message to Shima _“When you’re coming?”_ It’s a little past 8, but he need to make preparations.

He opened one of his drawer and took a supermarket plastic bag. “See this, Kuro. This cost me almost half of my monthly allowance, this supposed to make me taller!” Inside the packaging was a pair of sole made from transparent plastic-like material.[ _‘Add 3 to 5 centimeters to your height! Easy to use and discrete, adjust the height and place it inside your regular shoe!’_](http://image.dhgate.com/albu_237807477_00/1.0x0.jpg)

Rin took it out, examining the sole. It was quite soft and flexible. 5 centimeters is not even enough to be at Yukio’s level, but that’s all he could afford right now. Rin adjusted it to the maximum setting. Rin opened Yukio’s wardrobe and found a spare shoe as well as the spare exorcist overcoat. He smirked, “This is going to be **_perfect_**.” Or so he thought.

It’s difficult to walk with the height enhancer sole inside his shoe at first. After walking up and down the stairs for a while he finally managed to do so naturally. _How can girls wear high heels all the time?_ His body is a bit slimmer than his little brother, but the exorcist robe is doing its job to make him appear bigger. _When did Yukio grow to be that big anyway?_

The hardest part his hair. Hair cut are expensive and he won’t risk looking ridiculous by cutting it himself. Besides Yukio nagged him about hair cut for so many times now, complaining that it is ‘long and messy’. Cutting his hair now will be like ‘submitting’ to Yukio, big no. Rin used a jar of styling gel that he bought yesterday, it’s the same brand that Suguro used, so it should work. He save hair for the last touch.

Next is glasses. He took one from Yukio’s stash, standing in front of the mirror to look at himself. No. He can’t see anything. Everything is blurry and he is getting dizzy. Yukio’s glasses has always been thick, even since they are young. Rin hesitated for a few minutes before breaking the glass with Kurikara’s tip. “Forgive me, little brother!”. Yukio have so many glasses, he won’t miss this one. As long as he didn’t get too close no one will notice his glasses are actually glassless.

  
His phone rang once, a message from Shima. _“We’re coming at 12 to eat lunch, Shiemi-san is coming but Izumo-chan said she’s already got a plan. Too bad.”_

Rin replied with a quick _“Ok!”_ and went to the kitchen to whip up several portion of _Super Yellow Okumura Rin Special_ for lunch.

At 11.30 he finished everything, with the help of Ukobach, and started to dress up. The extra height provided by that cheap _as seen on TV_ goods are playing a big part in this. When he finally got his hair done and wear the glasses he admired himself in the mirror. Rin even stroked some poses. It looked cool as heck. Now he can't wait to pass the exorcist exam to get his own robe.

He also bought a fake ear toy, he used it to create make-shift concealment for his pointy ears. His hair covered most of it, so it looked quite convincing.

Now, for a final touch, he opened the drawer where Yukio kept his gun cleaning kit. There is a gun in there, but it is very light. Rin assumed it is an empty case and decided that it’s not dangerous to carry it around. Little details matters you know!

“How do I look, Kuro?” Rin crosses his arm with a wide grin.

  
**_You look like him, Rin! But don’t smile too wide, just a little!_**

  
As Rin tried to figure out how to do a _Yukio Face_ he heard a familiar voice calling from downstairs, “Okumura-kun! We’re here!”

“Oh, they are here! Alright!” He tried to suppress his giggles, “Oops! Almost forgot the most important thing!” Rin stopped in front of his desk and took a black marker. He dotted his face at the exact same location of Yukio’s moles. Rin remembered where they are because when they are young Yukio often asked his help to count. Ah, good old days when Yukio is not such a hardass.

  
“Ooo-kuuu-muuu-raaa-kuuuuun!” Shima’s voice echoed through the empty building.

“Coming!” Rin said with his _Yukio Voice._ He drew a deep breath and opened the door.

“E-eh? _Wakasensei_ … So-sorry for shouting.” Shima who almost hit Rin in the forehead when he tried to knock as Rin opened the window stared with wide eyes.

“Good afternoon, sensei!” Suguro greeted him with a small acknowledging bow, such a good student. Rin is holding down giggles with all his might.

“Okumura-kun told us to come and have lunch today!” Konekomaru added, smiling as well.

“Ah, my brother did mention that. Sorry, but he was not here at the moment. Meph—Mr. Pheles summoned him for a detention just now, probably causes some trouble again.” He sighed, like how Yukio usually sighed when he’s making trouble. He sighed because talking in Yukio’s polite tone and manner is hard!

“That’s too bad. Should we head back then?” Shima looked a little disappointed. Rin’s cooking is delicious.

  
“No, Shima—kun. My brother already cook some food for you guys, I—I[1] can heat the meal. How does that sound? My brother asked me to look over your homework as well since I have some free time.” Rin smiled, a subtle smile that doesn’t show any teeth, not his usual ear-to-ear grin.

  
“Did you caught a cold again, Sensei?” Suguro asked as they walked up the stairs, heading into yesterday’s dining room.

“Yeah, but I already took some pills as precautions.” Rin scratched his cheek. Suguro is a sharp one, must be careful.

“Your meister is Dragoon and Doctor, right? Must be nice to be able to treat yourself and never spend a dime on doctor visit…” Konekomaru added.

“It’s not like I actually hold a _real_ medical license. But I planned to get one after graduating high school.” Rin attempted to say _smart things_ that Yukio usually said when he asked about being a doctor. It worked so far, because nodded while looking at him with an awe.

“Oh, I remember that you’re the freshmen representative from our first day here!” Shima recalled their first day at the True Cross Academy. Being the representative means you scored the highest mark in the entrance exam.

“It’s nothing, really. I’m on the advanced placement class where everyone is very smart.” Rin remembered three girls from Yukio’s class that almost got cooked by Ukobach. Alright, maybe not _that_ smart.

“Why do you want to be a doctor? Isn’t the exorcist meister is enough?” Suguro tilted his head.

“My brother is very reckless, as you all might already know. When we are younger I can’t remember a day when he’s coming home without scrapped skin or bloodied nose. Fighting everyday like a delinquent.” Rin sighed, those are dark days. “I decided to be a doctor so that I can keep an eye on him. Go ahead and sit.”

“Aw, you’re such a good brother, I’ll trade my idiotic older brother for you, _wakasensei_.” Shima is thinking about his brother Kinzo.

  
As Rin moves to the kitchen they can hear another call, “Rin!”

“That must be Shiemi-san. I’ll let her in!” Shima stood up before Rin even turned around, winking.

 _Wow, perks of being Yukio I guess! They all are nice and polite!_ Rin grinned like an idiot because Suguro and Konekomaru can't see him from there. Ukobach already heated the meals and helping to carry the plates out. “Thanks.” He said, carrying the rest of it to the table.

“Here you go. My brother’s specials.” He placed it on the tables, then took a seat on the farthest end. Suguro’s stares are digging into him, he did not want to reveal too soon.

“Ah, Yuki-chan. Where is Rin?” Shiemi appeared with Shima, she took a seat near him.

“He got some detention with Sir Pheles.” Rin explained while trying to keep his face straight. Shiemi _do_ look at Yukio like he’s the eighth wonder of the world.

“Are you sick? I can bring you some medicinal tea from our shop if you want…” Shiemi looked worried. A light shade of red appears because Rin is getting flustered by the attention.

  
“N-Nii-san already brought me some pills.” He tried to smile, “Go ahead and eat, everyone. My brother prepared this since morning, too bad he can’t stay and eat.” He turned his gaze at the Kyoto Trio, who did not waste any more time and began to dig in.

  
“Uwah, this is delicious!” Konekomaru stated after his first bite. Rin’s cooking never fail to amaze him.

  
“It’s still hard to believe _that guy_ can make such a delicious meal.” Suguro added, this is one of the thing that he hates to acknowledge about Rin.

“Now, now. Everyone must at least have one thing that they are good at, Bon!” Shima knew how Suguro felt about it.

“And what exactly the thing that you are good at, Shima?” Suguro retorted without skipping a beat.

“That’s rude! I’m good at… Understanding girls, you know!”

“How come Kamiki-san still resent you the most?” Konekomaru rolled his eyes.

“Sensei, how about you, do you have any girls you like?” Shima suddenly turned to _Yukio_ in attempt to escape the conversation over there.

“Wha—” Rin swallowed too fast and choked on his egg, causing Shiemi to hand a glass of water in panic.

“Shima, that’s rude!” Suguro barked at Shima, veins popping up on his forehead.

“It’s alright, Suguro-kun. That question caught me off guard. Well, right now I’m too busy with my job, school, and missions, girls are out of the question.” He do like someone. Someone that is sitting beside him right now. Rin casually looked at Shiemi’s general direction, attempting to see a reaction. But there’s none.

“What about Kirigakure-sensei? You two are close!” Shima refused to drop the subject.

  
“She is a nightmare, she called me names and never miss a chance to _torment_ me.” Rin’s gaze darkened for a second. He learned about how much Yukio used to dislike Shura when they spent some time in the training room a while back.

“Really? Kirigakure-sensei is nice to us.” Shiemi mumbled to herself, trying to imagine how exactly she tormented Yukio.

The rest of the meal went more or less uneventful. Except Shima’s attempt to talk Shiemi into choosing ‘which one of the Okumura twins you think is more handsome'. It ended up with Shima getting smacked in the head by Suguro. Once they cleared the table, Rin stood up “Do you bring your homeworks?”

Everyone take out their book. This is the main reason why they agreed to come, after all. “We already finished most of it…” Suguro began to speak, but his voice only trailed.

“Of course. It’s alright. I’ll go to my room and fetch the materials…” Rin then turned to walk into their shared room, he planned to take _that_ map. It surely contain the answer of this week’s homework. He will put it back before Yukio even come home.

 ** _Rin, Yukio is going to be angry._** Kuro woke up when he saw Rin opening Yukio’s drawer.

  
“He will never know as long as no one told him, Kuro!” He grinned, taking the map and carried it out. “I can’t wait to see the look at their face when I corrected all their mistake, especially Suguro!” Rin giggled, speaking to Kuro that decided to follow him.

“Everyone, let’s beg—” Rin froze. Yukio is standing in front of their table, talking to Suguro which haven’t realize anything. Shima’s eyes widened when he saw _another Yukio_ walked in, his jaw dropped upon realization.

“Nii-sa—” Yukio, which also have no idea of what happening turned to face his brother.

  
_SLAP! CRACK!_

  
Rin slapped Yukio’s glasses upward, it hits the ceiling and broke, then landed on top of Yukio’s head. This felt very surreal to the cram school students, proven by how their jaws are now hanging wide open.

Rin gasped when he realize what he had done. Earlier he did not want Yukio to see him, so his hand moved on its own.

Yukio was still frozen, this is almost comical since it had happened before. He did not say anything, taking a spare glasses from his pocket and put it on. He looked at his brother from top to toe, slowly taking in what actually happened.

Rin let out a loud snort seeing that Yukio is now wearing double glasses. The broken one on top of his head and the spare one on his face. “Yukio—”

“What is the meaning of this?” Yukio’s face darkened and at that moment Rin began to regret everything. Yukio is scary when he is mad. He don’t have any power but the demon’s blood still runs in his vein.

“I can ex—”

  
The cram school student can only see Yukio’s back. But judging from Rin’s frightened expression they decided that it is for the best. They also create a mental note to never make the young teacher angry.

  
“You. Broke two of my glasses to pull this stunt.” Yukio pointed at the broken glasses on top of his head, then to the one in Rin’s face. “And you took the map? Don’t I make myself clear when I told you? Don’t. Touch. This. Map. Nii-san?”

  
“Kuro let’s go!” Rin turned his back and dashed to the window, planning to jump and escape. Unlucky for him, Yukio’s hand are faster. Yukio grabbed Rin’s tails and pulled it, causing the older twin yelped in pain.

  
“Oh, you’re dead, Nii-san. Don’t even think of running away.” Yukio pulled out his gun, loading it with one of the cartridge hanging on his belt with one swift motion.

  
_BANG! BANG! BANG! BANG!_

  
Four times he fired, the loud sound echoed through the big empty dining hall.

  
“Rin!”

  
“Okumura-kun!”

  
“Okumura!”

  
Different voices filled the room.

“Sensei—What have you done?!”

“Don’t worry. It’s just vitamin capsules.” Yukio said with a calm voice, his usual smile plastered on his face. He kept a whole cartridge filled with it after the incident with Shiemi months ago.

Yukio moved to the side, revealing Rin that curled in the floor. “But it fucking hurts when you get hit at this distance.”

“Damn you, Yukio! No swearing or I will slap your mouth!” Rin groaned loudly between his muffled groan of pain.

_BANG!_

Yukio shoot one more time and bent down to pick up the map. “So, everyone, do you need me to look over your homework?” He pulled a chair and sit down.

Everyone who still looked at Rin with wide eyes snapped back to reality.

“N-no, I already finished mine last night!” Shima is the first one to speak.

“Y-yeah, we are done!” Suguro added.

Konekomaru started nodding like mad when Yukio looked at him.

“What about you, Shiemi-san?” He smiled.

  
“N-no, Yuki-chan. I already finished…” She shook her head.

“If everyone is already finished why don’t we check it today to save time then?”

“NO!” Even Shiemi joined in the loud chorus of ‘No!’.

“See? Let me check it for you…” Yukio extended his hand, still with a smile. He then started correcting some mistakes as well as dictating notes for the students.

Rin slowly got up and pulled a chair beside Yukio, still holding his side where the bullets hit him. “Why are here anyway?! This supposed to be perfect if you come home at dinner like usual!” Rin took of Yukio’s coat and let it hang on the back of a chair beside him.

“The principal called me earlier. He told me to come home with a key right now because there is something _interesting_. I can see what he means now.”

“Damn clown, I’m gonna kill him someday!”

 

**Notes for the Chapter:**

> [1] Rin uses 'Ore' while Yukio uses 'Boku' to address themselves. 
> 
> I have a side story of what happened with Shima posted under this series soon (to make up for this unsatisfactory chapter) 
> 
> If you have any prompts just drop it in the comment, I'm planning to create some Okumura Twins one-shots for this series. 
> 
> Thanks for reading!


End file.
